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Unread 05-30-2009, 09:26 PM   #1
MEinSoCal
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WTF! i just changed spark plugs and now it idles really rough

it was running fine before, no CEL. i just decided to change my plugs due to high mileage. i tried 2 different brands of copper -- champion and bosch, and both had the same results. yes the plugs were properly gapped according to FSM and all bolts torqued to factory spec.

what the hell is happening here? it starts up like **** and idles very rough

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Unread 05-30-2009, 09:38 PM   #2
gatorayde
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Maybe you bumped a sensor or the coil rail became damaged.
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Unread 05-30-2009, 09:45 PM   #3
ZeeJay1997
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I'm going to list the things I can think of just in case you had a brain f*rt.

1. You crossed a plug wire
2. You broke a plug wire
3. A plug wires isn't seated good and arcing off the head. (look for blue spark at night)
4. You put the wrong plugs in it.
5. You cracked a plug
6. You cracked the distributor
7. You distributor cap is not seated properly
8. Your distributor is loose and you changed the timing (long shot)

Yikes, Does a 99 I6 have a rail???

Duh, bolts... of course it does dummy. Nevermind about the wires...
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Unread 05-30-2009, 09:46 PM   #4
gatorayde
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No wires or distributors on WJ's
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Unread 05-30-2009, 09:48 PM   #5
MEinSoCal
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Quote:
Originally Posted by ZeeJay1997 View Post
I'm going to list the things I can think of just in case you had a brain f*rt.

1. You crossed a plug wire
2. You broke a plug wire
3. A plug wires isn't seated good and arcing off the head. (look for blue spark at night)
4. You put the wrong plugs in it.
5. You cracked a plug
6. You cracked the distributor
7. You distributor cap is not seated properly
8. Your distributor is loose and you changed the timing (long shot)

Yikes, Does a 99 I6 have a rail???

Duh, bolts... of course it does dummy
yes i have a coil rail. i really wish it was a simpler distributor and spark plug wire setup
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Unread 05-30-2009, 09:53 PM   #6
ZeeJay1997
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Disregard the babble, I live in another era.
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Unread 05-30-2009, 09:59 PM   #7
Virmagicus
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Disregard the babble, I live in another era.
ZeeJay1997
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Unread 05-30-2009, 10:06 PM   #8
elmer_fud
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try disconnecting the battery for a while (30+ minutes) and see if it resets the computer and helps it run better
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Unread 05-30-2009, 10:14 PM   #9
the88thpianoman
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The coil rail is very sensitive. I hope that's not it, though.
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Unread 05-30-2009, 10:41 PM   #10
MEinSoCal
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Originally Posted by the88thpianoman View Post
The coil rail is very sensitive. I hope that's not it, though.
me too. i did kind of twist the wiring of the coil rail to move it out of the way. hopefully i didn't mess anything up
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Unread 05-30-2009, 11:37 PM   #11
Envygreen
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Go drive it for 5 minutes the computer will re-learn, If your gap was well worn its still using the old parameters
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Unread 05-31-2009, 08:44 AM   #12
4jeepers
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Go drive it for 5 minutes the computer will re-learn, If your gap was well worn its still using the old parameters
I second the motion!
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Unread 05-31-2009, 10:54 AM   #13
MEinSoCal
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UPDATE: so last night, after i changed to the 2nd set of spark plugs, i also cleaned out the throttle body and added 1/2 can of combustion cleaner. after going for a test drive, i got the CEL light to come on w/ 3 codes

0505 - IAC : i changed it with a new part from autozone (thank god they're open til midnite)
0123 - TPS : Throttle position sensor input above the maximum acceptable voltage
0108 - MAP : sensor input above maximum acceptable voltage.

i disconnected the battery to clear out the codes to see what would come back on. after replacing the IAC, the rough idle seemed like it was smoothed out. in fact the instructions said to drive the car with the engine warmed up, going 40mph to let the IAC adapt. did that and the its still running really rough, kind of like the engine is sputtering. can't even accelerate smoothly.

i'm almost tempted to replace the TPS next since my jeep is approaching 200K (and the part is only $45) and i'm sure the previous part is pretty damn old and has been used for a while. i'd hate to keep throwing parts if not needed.

on a side note, how do i troubleshoot a vacuum leak? where should i look? anyone have a pic of all the vacuum lines for a WJ 4.0L?

by the way, the CEL have not come back on... not yet at least
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Last edited by MEinSoCal; 05-31-2009 at 11:26 AM..
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Unread 05-31-2009, 05:34 PM   #14
wj03grandy
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man im have the exact same problem for sometime now and i cant figure it out.

i replace the IAC, and the TPS (code) and i get a code for small vaccum leak (code) that i CAN NOT FIND!
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Unread 05-31-2009, 05:45 PM   #15
Houndmaster1
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You can look for a vac leak with a can of carb cleaner, spray around the intake, any gasket on the intake ant t-body. If the engine rpm changes you can isolate and find it. If you prefer, propane works to. I prefer carb cleaner. Idealy you can smoke it, if you have a smoke machine. A party smoker with a rubber hose will work with a little rigging.
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